We hypothesize that abnormalities in the oral microbiome will be detectable on admission, and that these will also rapidly renormalize with abstinence and resumption of ordinary diet and oral hygiene. If not, the findings in this study could point to the need for other interventions, such as administration of probiotics. Twenty evaluable participants admitted to the Clinical Center for alcohol detoxification will be enrolled. All patients will be admitted under the Unit and Clinic Evaluation, Screening, Assessment, and Management protocol (14-AA-0181), which includes adults 18 years of age or older seeking treatment for severe alcohol use disorders. Oral (tongue brushings) and gut (stool) specimens will be collected daily until for the first week. And then once a week for 28 days. Demographic characteristics, detailed drinking and dietary histories, measures of addiction severity, comorbid mental disorders, and metabolic indicators of other disease will be collected for correlation with microbiological results. Dietary records will include use of probiotics. Exclusion criteria include use of antibiotics, corticosteroids or immunosuppressive agents within the past month. Informed consent will be obtained after consent for the screening and treatment protocol (14-AA-0181) and in accordance with policies protecting participants with impaired decision-making. Microbial identification will include 16S rRNA analysis and a validated Next Generation Sequencing analysis pipelines. Statistical comparisons between each patients oral and gut microbiome samples will be evaluated and all results from this population will also be compared to published microbiomes in both healthy volunteers as well as existing data from alcohol dependent individuals. Participants will be compensated for research-related discomfort and inconveniences in accordance with NIH guidelines. This study has finished accrual.